A Community and Forum For Aquaponic Gardeners
Charcoal as a media
Hey guys, I'm going to open this up for debate, as things are getting a little off topic on my personal system discussion. There have been questions as to the safety of charcoal as a media, and I'm sure there are questions out there regarding it's environmental impact. So let's let fly with the questions and hash this out. I'm definitely not the expert here, and I am hoping George will weigh in on the issues.
Personally I decided to use charcoal based on the fact that I have free access to wood, and needed a cheap and light media for use in a GB supported by a light stand that's not meant to support a lot of weight. I know that activated charcoal is used in aquaria as a filter media, so I'm pretty sure it's safe. That said we all know that many things from tropical fishkeeping don't transfer to aquaponics very well.
Replies to This Discussion
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Permalink Reply by TCLynx on
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Hay Paul, I expect you were right in the last comment you had made about it in your thread.
About the catchments where there were forest fires and the elevated merucry levels being due to things other than the charcoal itself.
Charcoal is used to filter drinking water for people too. And charcoal is often used in medicine as well like when some one ingests certain toxic things, charcoal is given to absorb the toxin before the body can absorb it.
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Permalink Reply by Paul Letby on
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I'll do a little copying and pasting from my system discussion:
Harold Sukhbir wrote:
Hi Paul,
I've been following your trial with interest over some time now. I know you've had discussions with somewhat qualified people previously but I've for a long time had a grave concern concerning coal for use as AP media.I don't want to come across as an alarmist or bearer of gloom and doom. I was silently hoping some of our experienced AP'ers in the know would have entered by this time to say something of the safety aspects of coal media. I felt obligated to share some of my reading on the subject. Here...........
coal-ash.pdf, 1.4 MBI really hoping I'm wrong about coal but just in case it's a real concern the better for all
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Hi Harold. I'm happy you've expressed your concern here, and that is a very important article. I'm thinking that the resident charcoal guru will weigh in on the issue as I'm not the expert. There are some pretty big differences between Charcoal and coal however:
http://en.wikipedia.org/wiki/Coal
http://en.wikipedia.org/wiki/Charcoal
Charcoal is approved for medical use, ie you can ingest it to help with poisoning! Try that with coal...
Hope this helps.
Possibly you are thinking of charcoal briquettes, which is not what Paul is using in his system. Commercial briquettes usually contain coal dust and other things which would be harmful in aquaponics. The wood charcoal that Paul is using is mostly carbon, with a little potash and trace elements and charcoal of that type has been used in agriculture with good results for thousands of years. You can easily make it and see the difference for yourself. I've used it in soil gardening and the comparison plantings convinced me and my neighbors of its benefits. I believe that, pound for pound, charcoal may nitrify more ammonia than other medias used in aquaponics but that is still to be investigated, as for as I know. Regards.
Harold Sukhbir said:I really hoping I'm wrong about coal but just in case it's a real concern the better for all
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Permalink Reply by Harold Sukhbir
Yes you're right about the difference between coal and charcoal. The article was not appropriate for discussion. Research has shown that wood burning can increase methylmercury in fish fivefold at toxic levels. Even though the mercury released is in small quantity the effect comes from biomagnification as it progresses up the food chain. Since AP has a similar Eco-system as nature I'm wondering if it will have the same effect.See these
http://www.jstor.org/pss/30051308
http://ec.europa.eu/environment/integration/research/newsalert/pdf/...
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Wow you're fast TCLynx! I'm still setting this all up. Ha ha. Yes, I was about to quote a bit from the paper that Harold sent me a link to.
"The authors show that forest fires, by altering soil and vegetation within burned catchments, affect
nutrient and Hg transport, which results in an enrichment of nutrients and Hg in the lake."So in effect just what you said. :)
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I will add that some of the disadvantages of charcoal are:
-it floats for a while
-black dust can get everywhere if you're not careful
-it's kinda brittle
Advantages:
-Handy if you can't find a pencil
-light!
-can be very cheap if you don't mind investing time
-already a proven filter media
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Here's one more negative as I try to wash my fingernails...
-stinkin black under fingernails hard to remove! :(
That said, you wouldn't be breaking charcoal into bits except when setting up a GB.
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Permalink Reply by George T on
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Paul, I'm really pleased that you are trying charcoal as a media. My results using crushed charcoal in soil have been very positive and I’m curious to see if that translates to AP. Many people have used and are using charcoal in soil. Several well known universities are studying the use of charcoal in soil and are publishing their findings. Any searches on biochar or terra preta will provide plenty of reading material on using charcoal in soil. In AP, however, you are one of the few, to my knowledge.
As to negatives, the dust, ash and floating issues could be easily dealt with outside by rinsing and soaking if you weren't frozen over. The smaller particles may end up in elsewhere in your system but chances are they'll simply be pumped back into the bed(s). Landscape cloth makes a good filter so maybe a filter around the base of the standpipe would be a good idea but then again you may deem unnecessary. The variety of particle sizes clearly distinguishes charcoal from other AP media. One could grade charcoal to capture uniform sizes but, as you pointed out, it’s brittle and breaks down. It remains to be seen if that is a problem. My experience with small particles of charcoal is that it continues to drain very well. Roots cling to charcoal particles in soil so that could be an issue for you later, when you remove plants.
Regarding the possibility that your charcoal could be contaminated in some way, it seems unlikely, provided that the wood you made the charcoal from was uncontaminated. For example, making charcoal from treated wood and then using that in your AP system would be a terrible idea because the substances used to treat wood are poisonous.
The porous structure of charcoal results in exponentially more surface area compared to gravel, for example. That, we hope, will make it a great media for AP. Bacteria inhabit the surface area so more surface area may result in more nitrification of ammonia. Wouldn’t it be a nice thing if one media bed could do the work of two?
I’d like to correct any impression that I’m an expert on this subject. I’ve read a bit about making charcoal and using it in soil and I have some experience in doing those things. It’s simply a subject I’m interested in, as I am in aquaponics. Good luck and keep us posted.
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Permalink Reply by Harold Sukhbir on
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Yes TC i also see mercury as not a significant problem in the use of charcoal. I think of greater concern with mercury contamination will be in volcanic rock and fish meal in fish food. However doing some additional reading shows that more mercury is released from burnt wood than the surrounding soil in this study done in the amazon. Apparently trees absorb it from the atmosphere and emit it when burnt.
http://www.mining.ubc.ca/faculty/meech/fire4nat.htm
Hay Paul, I expect you were right in the last comment you had made about it in your thread.
About the catchments where there were forest fires and the elevated merucry levels being due to things other than the charcoal itself.
Charcoal is used to filter drinking water for people too. And charcoal is often used in medicine as well like when some one ingests certain toxic things, charcoal is given to absorb the toxin before the body can absorb it.
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mercury in wood.doc, 76 KB
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Dave Donley over on BYAP has been experimenting with carcoal in his AP systems for a while now.
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Permalink Reply by Ryan Chatterson on
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The only problems I see are that
1) It's going to be binding some of the available nutrients for about the first month until the open bonding sites are bound.
2) Its going to be pretty brittle.
Other then that, it is super porous and works GREAT as a biological media. Just make sure to give it a super rinse before putting it in(Like everything else).
Of course you could always make a dedicated biofilter and fill it with the carbon, then plumb it into the system.
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Cool link TCLynx, thanks. It's nice to see I'm not the only one. :) Dave's option to buy the charcoal is much faster than making it yourself! That said I know exactly where the wood came from and get a little peace of mind over that.
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Odds are that you have better aquaponics charcoal since you've been extinguishing yours, expanding the pores, creating more surface area. Also, your inner firebug appreciates it.
Paul Letby said:Dave's option to buy the charcoal is much faster than making it yourself!
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Permalink Reply by Mike Creuzer on
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I read about the terra petra myself, and when I ran out of growbed aggregate, all I had left was some aquarium activated charcoal, so I gave it a try. I use pots in my grow bed so I can move plants around, so it's pretty easy for me to try something like this.
Youtube video of the start of the experiment. http://www.youtube.com/watch?v=tP8CHjN7jWs&list=PL07F12DC70...
The small sample size showed that the charcoal laced pot grew a little bit better than the plain pea gravel. But that could have been just because of the lighting, etc. Too small of a sample to show anything meaningful.
I just planted fresh seeds in a seasoned charcoal addendum grow media, so we shall see how it turns out. The seedlings are 2 weeks old, so no significant difference yet.
I stuck some metal into some of the pots to try to address iron deficiencies. The charcoal sticks to the iron like barnacles. It's the weirdest thing. I don't know if it's biological or chemical. I am trying to convince a local retired microbiologist to come check out my system and tell me what's all going on.
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